1. Field of the Invention
This invention relates to centrifugal pumps of the type commonly known as chopper pumps, which are configured to process solid waste materials such as medical waste, municipal waste and food-processing waste. Specifically, this invention relates to an impeller and chopper plate having a cutter bar structured for use in a chopper pump.
2. Description of Related Art
Various industries involve or require the processing of solid waste material into a form that can be disposed of in a suitable manner. Certain solid wastes containing or comprising, for example, plastics, metals, animal byproducts and other hard or stringy materials present a particular challenge to processing the material into a disposable form. Therefore, centrifugal pumps of the type known as chopper pumps are typically employed in processing such solid waste materials into a size that can be disposed of or processed further as needed.
Chopper pumps are typically characterized by having an impeller that is structured to contact a cutting element positioned adjacent the vanes of the impeller to exert a cutting or chopping action on the solid waste material entering the pump. A majority of the chopper pumps known in the industry further employ a booster impeller or chopper blade that also interacts with the cutting element positioned adjacent the vanes of the pump impeller to aid in chopping or cutting the waste material prior to entry of the material into the pump impeller. Examples of such pumps are disclosed in U.S. Pat. No. 3,973,866 to Vaughan, U.S. Pat. No. 4,840,384 to Dorsch and U.S. Pat. No. 6,190,121 to Hayward, et al.
When a booster or chopper blade is employed, the chopper blade is secured to the terminal end of the drive shaft and is rotated with the pump impeller. The chopper blade is spaced from the pump impeller by a stationary intake plate and the drive shaft extends through the center of the intake plate to engage the chopper blade. Similarly, a space is provided between the chopper blade and the intake plate.
The described configuration of known chopper pumps produces a central zone located at the eye of the pump impeller and about the hub of the chopper blade where solid material cannot be cut and fluid cannot be pumped, thereby reducing the flow efficiency and chopping efficiency of the pump. Moreover, stringy material can wrap around or become lodged about the hub of the chopper blade in many chopper pumps, thereby decreasing pump efficiency or potentially halting pumping operation altogether. Additionally, with chopping efficiencies reduced at the center or eye of the impeller, otherwise known as a “dead spot,” cutting must take place solely near the outside diameter of the impeller.
Thus, it would be advantageous to provide a chopper pump having an impeller and associated chopper plate which are designed to avoid the problems encountered with conventional chopper pumps where material becomes trapped near the eye of the impeller, and a chopper pump which provides improved flow efficiencies.